Issue facing in migrating Lucene.Net 3.0.3 to Lucene 4.8.0-beta00016

[Kant, Manish]

Hello Team,

I am migrating Lucene.Net 3.0.3 to Lucene 4.8.0-beta00016 but I see many APIs 
are breaking.
I am referring migration guide -
https://lucenenet.apache.org/docs/4.8.0-beta00014/api/core/migration-guide.html
https://lucenenet.apache.org/docs/4.8.0-beta00015/api/core/migration-guide.html
but still I see some information is not there.

Need some help to fix the build issues -

  1.  WhitespaceTokenizer - in doc it is mentioned WhitespaceTokenizer class  
is moved to different name space but when I use that namespace this call is not 
there.
  2.  Many methods are not suitable to override like -
     *   protected override void Dispose(bool disposing) - IndexSearcher
     *   public override void Search(Query query, Collector results) - 
IndexSearcher
  3.  MaxFieldLength - IndexWriter could not be found
     *   IndexWriter does not have a constructor for 5 parameters.
     *   GetReader() is missing
     *   Reopen() is missing from IndexReader

I have more build issues which I will ask later.

Thanks and Best Regards,
Manish